Combined study of segmental movements and motion of the centre of mass during adaptation on a split-belt treadmill

BACKGROUND AND AIM: Walking on a split-belt treadmill (each of the two belts running at different speed) has been proposed as an experimental paradigm to investigate the flexibility of the neural control of gait and as a form of therapeutic exercise for hemi-paretic patients[1]. However the scarcity of dynamic investigations both for segmental aspects and for the entire body system, represented by the Centre of Mass (CoM), challenges the validity of the available findings on split-gait. Thus, the aim of the present study is to describe the dynamic adaptation of healthy subjects in terms of segmental and CoM motion, using Gait Analysis on Force Treadmill [2]. The study intends to clarify the effect of "split-gait", underlining its differences with pathologic claudication. METHODS: Ten healthy adults walked on a split-belt treadmill mounted on force sensors, with belts running either at the same speed ('Tied Condition', TC) or at different speeds ('Split Condition', SC, 0.4 vs 0.8 m/s). For the study of segmental motion, the surface Electromyography (sEMG), sagittal power and work provided by ankle, the main engine of body propulsion, were simultaneously recorded. For the study of the CoM motion, the Total Energy (Etot) and the percentage of Recovery (%R), the index of efficiency of the pendulum-like mechanism, were simultaneously analyzed. Various tied/split walking sequences were requested. The study was approved by the Local Ethic Committee. RESULTS: In the SC, the segmental motion analysis revealed a marked asymmetry between the two sides. The work provided by the ankle was 4.8 times higher (in the 0.4 vs 0.8 m/s conditions, respectively) compared with the slower side, and 1.2 times higher compared with the same speed in the TC (0.6 m/s) [3]. Paradoxically, the analysis of the CoM revealed an increased efficiency of the pendulum mechanism, with a higher %R in SC with respect to the TC at the same speed. CONCLUSIONS: Split gait entails its own pattern of locomotion, very different from pathologic claudication. The faster leg mimics the paretic limb temporally, but the unimpaired limb from the spatial and dynamic point of view[3]. This must be considered when a therapeutic application is designed. REFERENCES:1. Helm et al. Phys Med Rehabil Clin N Am. 2015;26(4):703-13. 2. Tesio et al. Am J Phys Med Rehabil. 2008;87(7):515-26. 3. Tesio et al. Int J Rehabil Res. 2018;41(4):304-315

Walking on a split-belt treadmill induces a higher power output and a shorter step length from the faster leg in healthy subjects, with opposite (after)-effect lasting less than 5 minutes after exercise

Walking on a split-belt treadmill has been claimed as a possible treatment of pathologic step asymmetries: in particular, the step lengthening on the affected side [1]. Placing the paretic limb on the slower belt would increase this asymmetry, reverting to long-lasting symmetry after exposure (after-effect). These studies neglected the underlying dynamics. Recently, it has been demonstrated that this paradigm entails an opposite spatial and dynamic asymmetry in healthy subjects. The stance on the faster belt is shortened, thus mimicking the paretic step temporally. On the contrary, the step is shorter and more muscle power is produced [2]. This challenges the rationale of the previous researches. The present study aims at extending these findings by investigating the after-effect both on spatiotemporal step parameters and power output from the plantar flexors on either belt. METHODS Ten healthy adults (21-34 years, 1.61-1.91 m tall, 5 women) participated in the study. After a brief familiarization, participants walked on a force-sensorized split-belt treadmill with one belt running at 0.4 m s-1 and the other belt running at 1.2 m s-1 (split condition) for 15 minutes and then, with no interruption, with the belts running at the same velocity (0.4 m s-1, tied condition) for other 5 minutes. The dominant lower limb was assigned to the faster belt. Kinematic data were recorded through an optoelectronic system as per the Davis anthropometric model. Joint sagittal power was computed by multiplying the moment generated by the ground reaction forces at the joints, times the rotation speed. All signals were simultaneously recorded [2]. The study was approved by the Local Ethics Committee. RESULTS Consistently with previous studies [3], during the split condition, the step length on the slower belt was longer, reaching gradually about 130% of the opposite step length. Ankle peak power attained about 15% of that observed on the opposite side. During the following tied condition, the step length on the formerly slower belt initially shortened by about 65% (after-effect), compared to the opposite step, and returned to values similar to that of the opposite side within 5 minutes. During this transition phase, ankle peak power gradually increased by up to 50% compared to baseline. On the formerly faster belt, step length did not change, while ankle peak power suddenly dropped to the contralateral level (Figure 1). Figure 1 Stride by stride plots (moving average, time-window 30 strides) of step length (upper panel) and ankle power (lower panel) from one representative subject (woman, 21 years, 1.65 m tall, body mass 60 kg) walking on a split-belt treadmill with the dominant lower limb on the faster belt (red) and the nondominant lower limb on the slower belt (blue). Strides from 1 to 867 refer to the split condition, and stride from 868 to 1025 refer to the following tied condition. DISCUSSION The increase in plantar flexor power on the faster belt, despite the shorter stance period and length, may reflect the priority need to counteract the backward drag from the faster belt, with respect to the slower one. This adaptation does not seem to lead to substantial learning, given that an after-effect, both on step length and ankle peak power, is only seen during the 5 minutes following split walking. In pathologic claudication, placing the affected lower limb on the faster belt might represent an effective form of \u201cforced-use\u201d [4], as far as enhanced power is requested. Long term effects remain questionable

High-throughput microfluidic platform for adherent single cells non-viral gene delivery

The widespread use of gene therapy as a therapeutic tool relies on the development of DNA-carrying vehicles devoid of any safety concerns. In contrast to viral vectors, non-viral gene carriers show promise in this perspective, although their low transfection efficiency leads to the necessity to carry out further optimizations. In order to overcome the limitations of traditional macroscale approaches, which mainly consist of time-consuming and simplified models, a microfluidic strategy has been developed to carry out transfection studies on single cells in a high-throughput and deterministic fashion. A single cell trapping mechanism has been implemented, based on the dynamic variation of fluidic resistances. For this purpose, we designed a round-shaped culture chamber integrated with a bottom trapping junction, which modulates the hydraulic resistance. Several layouts of the chamber were designed and computationally validated for optimization of the single cell trapping efficacy. The optimized chamber layout was integrated in a polydimethylsiloxane (PDMS) microfluidic platform presenting two main functionalities: (i) 288 chambers for trapping single cells, and (ii) a serial dilution generator with chaotic mixing properties, able to deliver to the chambers both soluble factors and non-diffusive particles (i.e., polymer/DNA complexes, polyplexes) under spatio-temporally controlled chemical patterns. The devices were experimentally validated and allowed the trapping of individual human glioblastoma–astrocytoma epithelial-like cells (U87-MG) with a trapping efficacy of about 40%. The cells were cultured within the device and underwent preliminary transfection experiments using 25 kDa linear polyethylenimine (lPEI)-based polyplexes, confirming the potentiality of the proposed platform for the future high-throughput screening of gene delivery vectors and for the optimization of transfection protocols

Microfluidic Platform for Adherent Single Cell High-Throughput Screening

This paper was presented at the 4th Micro and Nano Flows Conference (MNF2014), which was held at University College, London, UK. The conference was organised by Brunel University and supported by the Italian Union of Thermofluiddynamics, IPEM, the Process Intensification Network, the Institution of Mechanical Engineers, the Heat Transfer Society, HEXAG - the Heat Exchange Action Group, and the Energy Institute, ASME Press, LCN London Centre for Nanotechnology, UCL University College London, UCL Engineering, the International NanoScience Community, www.nanopaprika.eu.Traditionally, in vitro investigations on biology and physiology of cells rely on averaging the responses eliciting from heterogeneous cell populations, thus being unsuitable for assessing individual cell behaviors in response to external stimulations. In the last years, great interest has thus been focused on single cell analysis and screening, which represents a promising tool aiming at pursuing the direct and deterministic control over cause-effect relationships guiding cell behavior. In this regard, a high-throughput microfluidic platform for trapping and culturing adherent single cells was presented. A single cell trapping mechanism was implemented based on dynamic variation of fluidic resistances. A round-shaped culture chamber (Φ=250μm, h=25μm) was conceived presenting two connections with a main fluidic path: (i) an upper wide opening, and (ii) a bottom trapping junction which modulates the hydraulic resistance. Several layouts of the chamber were designed and computationally validated for the optimization of the single cell trapping efficacy. The optimized chamber layouts were integrated in a polydimethylsiloxane (PDMS) microfluidic platform presenting two main functionalities: (i) 288 chambers for trapping single cells, and (ii) a chaoticmixer based serial dilution generator for delivering both soluble factors and non-diffusive molecules under spatio-temporally controlled chemical patterns. The devices were experimentally validated and allowed for trapping individual U87-MG (human glioblastoma-astrocytoma epithelial-like) cells and culturing them up to 3 days

The path curvature of the body centre of mass during walking as an index of balance control in patients with Multiple Sclerosis

BACKGROUND AND AIM: The path curvature of the centre of mass (CM), mechanically representative of the whole body system, may provide hints to detection of fall risk during walking. Here, an example is taken from results of an ongoing controlled study. It shows the comparison between the CM path in a healthy subject and in a fully autonomous patient with Multiple Sclerosis (MS). METHODS: A representative healthy subject (woman, 26 years, 1.55 m tall) and a MS patient (woman, 34 years, 1.65 m tall, with very mild left hemiparesis) are presented. Subjects walked on a force-sensorized treadmill (1) at 0.6 m/s. Data were averaged across 6 subsequent strides. The 3D displacements of the CM were computed via double integration of the ground reaction forces (Cavagna's Method). The path curvature of the CM during one stride was computed according to the Frenet-Serret formula (2). The instantaneous efficiency of the kinetic-potential, pendulum-like energy transfer of the CM was also computed (percent recovery, R: 100%=complete recovery, i.e. fully passive CM translation) (3). RESULTS: The left and right panels refer to the control and the MS subject, respectively. In the upper set of panels the human sketches on top of the figure help identifying the stride phases (% cycle) and give a frontal and a sagittal perspectives. The first and second rows of curves from the top give the instantaneous R and the path curvature of the CM during one stride. Each step begins with the single stance of the front leg (R=right; L=left). The horizontal bars under the curves mark the double and the single stance phases (continuous and dashed lines, respectively; grey tract=left step). The lower set of panels (closed curves) gives the planar projections of the CM path during the same stride. The space-time correspondence between the 2 sets of curves is facilitated by the shared A-D labeling of peak curvatures and the shared graphic conventions (dashed line=single stance; gray tract=left step). In both steps the curvature is peaking when R suddenly drops from 100 to 0, demonstrating that the passive pendulum-like mechanism of translation is briskly substituted by a short lasting, fully muscle-driven, propulsion. The highest peaks (A and C) are coincident with the lateral redirection during single stance. Of note, the patient's CM path is characterized by a 10-fold higher C peak (single stance, paretic-to-unaffected side redirection). This may be interpreted as a feature of "escape" limp, barely perceivable by clinical observation, when seen from the perspective of the body CM on the horizontal plane (bottom curves). CONCLUSIONS: Increased curvature peaks may reveal the attempt to shorten the stance on the affected side yet, placing at risk the lateral stability of the body. REFERENCES:[1] Tesio L, Rota V, Am J Phys Med Rehabil 2008;87:515-526 [2] Tesio L et al, J Biomech 2011;44:732-740 [3] Cavagna GA, J Appl Physiol 1975;39:174-179

Measuring voluntary activation of the quadriceps femoris during isokinetic concentric contractions

BACKGROUND: It is known that Voluntary Activation (VA) of muscles may be lower during isokinetic concentric (CON) contractions than during isometric (ISOM) contractions, and that it may be further decreased in various motor impairments. OBJECTIVE: The aim of this study was to validate the Interpolated Twitch Technique (ITT) for quantifying VA of the Quadriceps femoris during CON contractions (knee extension at 60 and 120_/s, CON60 and CON120, respectively). METHODS: Pairs of electrical stimuli were delivered to the Quadriceps femoris of twenty-two healthy subjects at 50_ of knee flexion. Participants were instructed to exert five different levels of effort in decreasing order between 100% and 20% maximal voluntary efforts in ISOM and CON contractions. RESULTS: Through a linear regression model, a significant relationship between measures of VA and moment was observed for all the three contraction conditions: slopes (95% confidence intervals) = 1.04 (0.98\u20131.11), 0.96 (0.89\u20131.02) and 0.84 (0.78\u20130.91); intercepts = - 5.22 (\u2013 8.61\u2013 \u20131.83), 4.16 (0.71\u20137.62) and 14.58 (10.76\u201318.39), for ISOM, CON60 and CON120 contractions, respectively. This supported the validity of the method. CONCLUSIONS: It is concluded that ITT can be a valid method for measuring VA during CON contractions, potentially useful both in sports and rehabilitation studies

Limping on split-belt treadmills implies opposite kinematic and dynamic lower limb asymmetries

Walking on a split-belt treadmill (each of the two belts running at a different speed) has been proposed as an experimental paradigm to investigate the flexibility of the neural control of gait and as a form of therapeutic exercise. However, the scarcity of dynamic investigations challenges the validity of the available findings. The aim of the present study was to investigate the dynamic asymmetries of lower limbs of healthy adults during adaptation to gait on a split-belt treadmill. Ten healthy adults walked on a split-belt treadmill mounted on force sensors, with belts running either at the same speed ('tied' condition) or at different speeds ('split' condition, 0.4 vs. 0.8 or 0.8 vs. 1.2\u2009m/s). The sagittal power and work provided by ankle, knee and hip joints, joint rotations, muscle lengthening, and surface electromyography were recorded simultaneously. Various tied/split walking sequences were requested. In the split condition a marked asymmetry between the parameters recorded from each of the two lower limbs, in particular from the ankle joint, was recorded. The work provided by the ankle (the main engine of body propulsion) was 4.8 and 2.2 times higher (in the 0.4 vs. 0.8, and 0.8 vs. 1.2\u2009m/s conditions, respectively) compared with the slower side, and 1.2 and 1.1 times higher compared with the same speed in the tied condition. Compared with overground gait in hemiplegia, split gait entails an opposite spatial and dynamic asymmetry. The faster leg mimics the paretic limb temporally, but the unimpaired limb from the spatial and dynamic point of view. These differences challenge the proposed protocols of split gait as forms of therapeutic exercise

Crouch gait can be an effective form of forced-use/no constraint exercise for the paretic lower limb in stroke

In hemiplegic gait the paretic lower limb provides less muscle power and shows a briefer stance compared with the unaffected limb. Yet, a longer stance and a higher power can be obtained from the paretic lower limb if gait speed is increased. This supports the existence of a 'learned non-use' phenomenon, similar to that underlying some asymmetric impairments of the motion of the eyes and of the upper limbs. Crouch gait (CG) (bent-hip bent-knee, about 30 degrees minimum knee flexion) might be an effective form of 'forced-use' treatment of the paretic lower limb. It is not known whether it also stimulates a more symmetric muscle power output. Gait analysis on a force treadmill was carried out in 12 healthy adults and seven hemiplegic patients (1-127 months after stroke, median: 1.6). Speed was imposed at 0.3 m/s. Step length and single and double stance times, sagittal joint rotations, peak positive power, and work in extension of the hip, knee, and ankle (plantar flexion), and surface electromyography (sEMG) area from extensor muscles during the generation of power were measured on either side during both erect and crouch walking. Significance was set at P less than 0.05; corrections for multiplicity were applied. Patients, compared with healthy controls, adopted in both gait modalities and on both sides a shorter step length (61-84%) as well as a shorter stance (76-90%) and swing (63-83%) time. As a rule, they also provided a higher muscular work (median: 137%, range: 77-250%) paralleled by a greater sEMG area (median: 174%, range: 75-185%). In erect gait, the generation of peak extensor power across hip, knee, and ankle joints was in general lower (83-90%) from the paretic limb and higher (98-165%) from the unaffected limb compared with control values. In CG, peak power generation across the three lower limb joints was invariably higher in hemiparetic patients: 107-177% from the paretic limb and 114-231% from the unaffected limb. When gait shifted from erect to crouch, only for hemiplegic patients, at the hip, the paretic/unaffected ratio increased significantly. For peak power, work, sEMG area, and joint rotation, the paretic/unaffected ratio increased from 55 to 85%, 56 to 72%, 68 to 91%, and 67 to 93%, respectively. CG appears to be an effective form of forced-use exercise eliciting more power and work from the paretic lower limb muscles sustained by a greater neural drive. It also seems effective in forcing a more symmetric power and work from the hip extensor muscles, but neither from the knee nor the ankle

Community-based rehabilitation program for cerebral PALSY (CP) children in North Uganda

Background: CP is a common neurologic disease in children, with a worldwide estimated prevalence of 93 million. Data on the African context are limited. Purpose: This study was aimed at evaluating the efficacy of a mixed outpatient/home physiotherapy program in children with CP admitted to St. Mary's Lacor Hospital (Gulu), the reference center of north Uganda. Methods: This is an observational, uncontrolled, prospective study. All children with CP (aged from 0.5 to 12 years) admitted in the Physiotherapy Unit from January to December 2017 were enrolled. A written consent form (English or Acholi language) was obtained from the mother/ caregiver. Each patient was evaluated at baseline and every two weeks for three months. CP sub-types were defined according to Surveillance of Cerebral Palsy in Europe classification. The child\ub4s abilities were staged through the Gross Motor Function Classification System Expanded and Revised (GMFCS-E&R; scale from I to V, the higher the worse). Changes in motor function were measured through the 66-item version (GMFM-66; scores ranging from 0 to 100, the higher the better). At baseline and subsequent visits, Bobath treatment was applied for 30 minutes by an experienced physiotherapist, who trained the caregiver on customized home exercises following a diary prescription. The functional status reported by the caregiver and the overall compliance were assessed. Changes in GMFCS-E&R and GMFM-66 at 6 and 12 weeks were recorded. The normality of score distributions was tested (Shapiro-Wilks). If confirmed, repeated ANOVA modeling was applied to scores across time points. Results: Fifty-two consecutive children were enrolled (mean age 2.2 years, range 0.5-9.9). Spastic bilateral (19 patients, 36%) and dystonic (16, 31%) were the most common CP sub-types. The main cause of CP were asphyxia during the delivery (26 cases, 50%) and cerebral malaria (10, 19%). Thirty-three/52 cases (67%) presented level V GMFCS-E&R. GMFM-66 mean score at baseline was 19.86 range: 0-52.9. Seventeen/52 (33%) children were assessed at 6 and/or 12 weeks, while 35 (67%) missed at least three study visits (reasons: 28 transportation cost, 2 remote home, 4 other). In 16/17 (94%) patients home exercises were performed correctly. The GMFM-66 mean score increased from 14.8 at baseline to 20.4 and to 24.9 at 6 weeks (p=0.02) and 12 weeks (p=0.00), respectively. The improvement was observed irrespectively from CP sub-type or cause of disability. Conclusion(s): Although on a small number of patients, this study suggests that a mixed outpatient/home physiotherapy program can improve CP disability in compliant children treated in a developing country, like north Uganda. The high drop-out rate and its causes point towards the need for implementing local community programs and/or transport facilities. Implications: These results suggest that a mixed outpatient/home physiotherapy program can benefit children with CP living in developing countries and strengthen the need of a policy aimed at improving the access to the physiotherapy service. In addition, they confirm that neurological damage during the assisted delivery is the major cause of CP in this conte

Three-dimensional path of the body centre of mass during walking in children : an index of neural maturation

Few studies have investigated the kinematic aspects of the body centre of mass motion, that is, its three-dimensional path during strides and their changes with child development. This study aimed to describe the three-dimensional path of the centre of mass in children while walking in order to disentangle the effect of age from that of absolute forward speed and body size and to define preliminary pediatric normative values. The three-dimensional path of the centre of mass during walking was compared across healthy children 5-6-\u2009years (n\u2009=\u20096), 7-8\u2009years (n\u2009=\u20096), 9-10\u2009years (n\u2009=\u20095), and 11-13\u2009years of age (n\u2009=\u20095) and healthy adults (23-48\u2009years, n\u2009=\u20096). Participants walked on a force-sensing treadmill at various speeds, and height normalization of speed was conducted with the dimensionless Froude number. The total length and maximal lateral, vertical, and forward displacements of the centre of mass path were calculated from the ground reaction forces during complete strides and were scaled to the participant's height. The centre of mass path showed a curved figure-of-eight shape. Once adjusted for speed and participants' height, as age increased, there was a decrease in the three-dimensional parameters and in the lateral displacement, with values approaching those of adults. At each step, lateral redirection of the centre of mass requires brisk transient muscle power output. The base of support becomes relatively narrower with increasing age. Skilled shortening of the lateral displacement of the centre of mass may therefore decrease the risk of falling sideways. The three-dimensional path of the centre of mass may represent maturation of neural control of gait during growth.This is an open-access article distributed under the terms of the Creative Commons Attribution-Non Commercial-No Derivatives License 4.0 (CCBY-NC-ND), where it is permissible to download and share the work provided it is properly cited. The work cannot be changed in any way or used commercially without permission from the journal